Various oral medications have been manufactured in the form of so called caplets, which can be swallowed by patients during their regiment of taking medication. Caplets, however, are not as easily swallowed by patients as capsules having, for example, a gelatin coating. Additionally, capsule coatings are desirable over caplets since the coatings provide a neutral taste in contrast to caplets per se which sometimes contain pharmaceutical substances that taste, for example, bitter. Thus, patients, in particular children, refuse to swallow such caplets per se. Attempts have therefore been made to encapsulate caplets in a capsule by means of a gelatin cover.
U.S. Pat. No. 4,867,983 to Berta describes a method for double dipping gelatin coated caplets. The method provides a procedure for coating solid cores, such as caplets, with a first gelatinous coating on one end, and then with a second gelatinous coating on the other end which is thicker than the first, to simulate the interlocking halves of a hollow capsule. The second, thicker gelatinous coating can be provided with a single gelatin coating from a bath having a higher viscosity than the bath used to provide the first gelatinous coating. Alternatively, the second gelatinous coating can be provided by double dipping to provide layers of gelatinous material or gelatin. This known coating is disadvantageous in that the gelatinous coating and the color distribution is not uniformly distributed over the caplets by this process. Moreover, an overlapping of the different coatings results in color changes of the coatings. Additionally, the dip margins obtained by the known process tend not to be straight. Furthermore, the coatings according to the above patent chip off under stress if the coated caplets are stored under dry conditions and/or high temperature. Finally, the dip coating process of U.S. Pat. No. 4,867,983 is time consuming and expensive.
From U.S. Pat. No. 5,081,822 to Boyd et al, an automatic caplet filler is known for filling normal gelatin capsules with caplets. The capsules formed by this automatic caplet filler, however, are disadvantageous in that they can be easily manipulated. Sealing of the capsules has to be effected by means of an additional gelatin strip or by gluing of the caplets in the capsule with an adhesive, as e.g. described in U.S. Pat. No. 4,928,840 or European Patent Application No. 0435726. This further treatment of the capsules may have the effect that substances other than the medication are encapsulated in the capsule. If on one hand a water-based adhesive is used for gluing the capsule halves together, the capsule as well as the caplet may be deformed. If on the other hand, an adhesive containing an organic solvent is used, a brittleness of the capsule will be the result. Finally, if the capsule halves are connected with each other by means of a heat shrinking process, a visible gap will remain between the capsule halves.
It is therefore the object of the present invention to provide a method for encapsulating caplets in a capsule in a tamper-proof form. It is yet another object of the invention to provide a cost-effective process for easily manufacturing tamper-proof solid dosage forms. It is yet another object of the present invention to provide a solid dosage form comprising a caplet covered by a capsule. It is yet another object of the present invention to provide a pharmaceutical dosage form having a greater resistance to breaking than known products. A further object of the present invention is to provide a tamper-proof solid dosage form.